00_scattered.rb

#!/usr/bin/env ruby

require "fileutils"

class ScatteredFile
  attr_writer :filelist

  def initialize(file_template)
    @file_template = file_template
    @filelist = []
  end

  def write(file_key, log)
    filename = @file_template % file_key

    f = @filelist.find {|f| f.path == filename }
    @filelist.reject! {|f| f.path == filename }

    if f.nil?
      begin
        f = File.new(filename, "a+")
      rescue Errno::EMFILE => e
        @filelist.delete_at(0)&.close

        retry
      end
    end

    f.puts log

    @filelist << f
  end

  def close
    @filelist.map{|f| f.close }
  end
end

FileUtils.mkdir_p "./tmp"

scatterd_file = ScatteredFile.new "tmp/tmp_%05d.txt"

(1...10000).each {|i|
  file_key = i

  scatterd_file.write file_key, i
}

scatterd_file.close

01_result

$ ruby scattered.rb

$ ls -1 tmp/
tmp_00000.txt
tmp_00001.txt
tmp_00002.txt
tmp_00003.txt
tmp_00004.txt
...
tmp_09995.txt
tmp_09996.txt
tmp_09997.txt
tmp_09998.txt
tmp_09999.txt

$ cat tmp/tmp_09999.txt
9999